Unless otherwise indicated herein, the information described in this section is not itself prior art to the claims and is not admitted to be prior art by inclusion in this section.
A typical wireless communication system may include one or more base stations, each radiating to define one or more coverage areas, such as cells and cell sectors, in which user equipment devices (UEs) such as cell phones, tablet computers, tracking devices, embedded wireless modules, and other wirelessly equipped communication devices, can operate. Further, each base station of the system may then be coupled or communicatively linked with network infrastructure such as a switch or gateway that provides connectivity with one or more transport networks, such as the public switched telephone network (PSTN) and/or the Internet for instance. With this arrangement, a UE within coverage of the system may thus engage in air interface communication with a base station and thereby communicate via the base station with various remote network entities or with other UEs served by the system.
In general, a wireless communication system may operate in accordance with a particular air interface protocol or radio access technology, with communications from a base station to UEs defining a downlink or forward link and communications from the UEs to the base station defining an uplink or reverse link. Examples of existing air interface protocols include, without limitation, Orthogonal Frequency Division Multiple Access (OFDMA) (e.g., Long Term Evolution (LTE) or Wireless Interoperability for Microwave Access (WiMAX)), Code Division Multiple Access (CDMA) (e.g., 1×RTT and 1×EV-DO), Global System for Mobile Communications (GSM), WI-FI, and BLUETOOTH. Each protocol may define its own procedures for registration of UEs, initiation of communications, handoff between coverage areas, and functions related to air interface communication.
In accordance with the air interface protocol, each of the one or more coverage areas of such a system may operate on one or more carrier frequencies and may define a number of air interface channels for carrying information between the base station and UEs. By way of example, each coverage area may define a pilot channel, reference channel, or other resource on which the base station may broadcast a pilot signal, reference signal, or the like that UEs may detect as an indication of coverage and may measure to evaluate coverage strength. Further, each coverage area may define a downlink control channel for carrying system information, page messages, and other control signaling from the base station to UEs, and an uplink control channel for carrying service requests and other control signaling from UEs to the base station, and each coverage area may define downlink and uplink traffic channels or the like for carrying bearer traffic between the base station and UEs.
When a UE initially enters into coverage of a wireless communication system (e.g., powers on in coverage of the system), the UE may detect a reference signal and read system information broadcast from a base station and may engage in a process to register itself to be served by the base station and generally by the system. For instance, the UE may transmit an attach message on an uplink control channel to the base station, and the base station and/or supporting infrastructure may then responsively authenticate and authorize the UE for service, establish a record indicating where in the system the UE is operating, establish local profile or context records for the UE, and provide an attach accept message to the UE. Thereafter, the UE may then be served by the system in an idle mode or a connected/active mode. In the idle mode, the UE may monitor a downlink control channel to detect page messages and other information regarding incoming communications and may similarly transmit uplink control signaling to initiate communications or for other reasons. In the connected/active mode, the UE may continue to monitor the downlink control channel and may have particular traffic channel resources assigned by the system, which the UE may use to engage in communication of bearer traffic and the like.
When a UE is served in a particular base station coverage area, the UE may also regularly monitor the reference signal strength in its serving coverage area and in neighboring coverage areas of the system, in an effort to ensure that the UE operates in the best (e.g., strongest) coverage area. In order to monitor the reference signal strength in neighboring coverage areas, the UE may need to pause its operation with and tune away from its serving base station. This tuning away may be necessary, for instance, if the serving base station operates on a different carrier frequency than a neighboring base station, as the UE may need to tune away from its serving carrier frequency to communicate on another carrier frequency with the neighboring base station. Further, the tuning away may be necessary if the serving base station operates on a different air interface protocol than the neighboring base station, as the UE may need to switch between radio interfaces in order to communicate on another air interface protocol with the neighboring base station.
To facilitate the UE tuning away from its serving base station to monitor the reference signal strength in neighboring coverage areas, the serving base station may schedule tune-away times. During the scheduled tune-away times, the serving base station may stop transmitting data to the UE, so the UE can tune away from the serving base station to scan for other coverage and/or monitor the reference signal strength in other coverage areas without missing any data from the serving base station. This may be referred to as a normal discontinuous reception (DRX) mode. The tune-away times may be scheduled in response to detecting a period of inactivity in communication between the UE and the serving base station, they may be scheduled when the serving base station has no remaining data to transmit to the UE, or they may be scheduled at regularly recurring times, among other possibilities.
If the UE detects threshold weak coverage from its serving coverage area and sufficiently strong coverage from another coverage area, the UE may then engage in a handover process by which the UE transitions to be served by the other coverage area. In the idle mode, the UE may do this autonomously and might re-register in the new coverage area. Whereas, in the connected/active mode, the UE may report signal strengths to its serving base station when certain thresholds are met, and the base station and/or supporting infrastructure may work to hand the UE over to another coverage area such as a neighboring base station.
In order to hand the UE over to the neighboring base station, the serving base station may require certain identifying information associated with the neighboring base station, such as an enhanced cell global identity (ECGI). If the serving base station does not already have access to the identifying information, then the UE may need to obtain the information from the neighboring base station and report it to the serving base station. In situations where the handover is being carried out while the UE is operating in the connected/active mode, the UE may need to tune away from the serving base station to obtain the identifying information from the neighboring base station.